* {
	margin: 0;
	padding: 0;
}

html, body {
	width: 100%;
}

main {
	position: relative;
	width: 959px;
	margin: 0 auto;
}

header {
	background: black;
	color: white;
	font-size: 56px;
	height: 80px;
	line-height: 80px;
	padding-left: 20px;
}

boxes {
	padding: 20px 0;
}

box {
	width: 22%;
	height: 200px;
	display: block;
	float: left;
}

#box1 {
	background: red;
	margin: 20px 4% 0 0;
}

#box2 {
	background: skyblue;
	margin: 20px 4% 0 0;
}

#box3 {
	background: green;
	margin: 20px 4% 0 0;
}

#box4 {
	background: orange;
	margin: 20px 0 0 0;
}

footer {
	font-size: 14px;
	color: gray;
	text-align: center;
	height: 22px;
	line-height: 22px;
	border-top: #ddd 1px solid;
	margin-top: 20px;
}

@media only screen and (min-width: 768px) and (max-width: 959px) {
	main {
		width: 100%;
		margin: 0;
	}
	header {
		font-size: 42px;
		height: 60px;
		line-height: 60px;
		padding-left: 15px;
	}
	box {
		width: 30%;
		height: 240px;
	}
	#box1 {
		margin: 25px 5% 0 0;
	}
	#box2 {
		margin: 25px 5% 0 0;
	}
	#box3 {
		margin: 25px 0 0 0;
	}
	#box4 {
		margin: 25px 0 0 0;
	}
}

@media only screen and (min-width: 321px) and (max-width: 767px) {
	main {
		width: 100%;
		margin: 0;
	}
	header {
		font-size: 36px;
		height: 48px;
		line-height: 48px;
		padding-left: 10px;
	}
	box {
		width: 45%;
		height: 225px;
	}
	#box1 {
		margin: 20px 10% 0 0;
	}
	#box2 {
		margin: 20px 0 0 0;
	}
	#box3 {
		margin: 20px 10% 0 0;
	}
	#box4 {
		margin: 20px 0 0 0;
	}
}

@media only screen and (max-width: 320px) {
	main {
		width: 100%;
		margin: 0;
	}
	header {
		font-size: 24px;
		height: 36px;
		line-height: 36px;
		padding-left: 6px;
	}
	box {
		width: 100%;
		height: 240px;
	}
	#box1 {
		margin: 20px 0 0 0;
	}
	#box2 {
		margin: 20px 0 0 0;
	}
	#box3 {
		margin: 20px 0 0 0;
	}
	#box4 {
		margin: 20px 0 0 0;
	}
}